The present invention relates to self-contained breathing apparatus such as may be worn to sustain the respiration of its user in noxious or oxygen-depleted environments. Such apparatus conventionally includes a portable source of breathing gas (e.g. a compressed air cylinder) and breathing interface means (e.g. a full or partial facemask) through which the breathing gas is in use supplied from said source to the respiratory passages of the user at a regulated rate.
In the case of self-contained open-circuit compressed air breathing apparatus it is usual for the air cylinder(s) to be carried on the back of the user, being mounted for this purpose on a plate or frame attached to a body harness comprised of strong webbing which passes over the user's shoulders and around his waist. As an alternative to this form of harness, it is known to support the cylinder on the back of a jerkin-type garment. Breathing sets are also known where an air cylinder is slung by a strap across one shoulder to be worn at the hip, but this arrangement is only suitable for relatively small and light cylinders, consequently providing very short endurance. A back-carrying harness arrangement is generally preferred because the weight of the cylinder(s) is distributed symmetrically and at a position which impedes the movements of the user the least.